Under a new fee system being considered by county growth management officials, a house in Lutz would be charged a "mobility fee" that is twice as much as one built in the University Area. In Wimauma, which is 30 miles from downtown Tampa, the fee would be three times higher than in Brandon.

The new fees would pay for transportation projects throughout the county. They were unveiled last week when county planners discussed the fees with developers and their consultants. Although they're far from getting approved, some consultants were already fretting about the fees.

"We need to consider the economy," said Biff Craine, a land use attorney. "We need to phase them in rather than kill any type of recovery in the housing industry."

Developers in Hillsborough County aren't used to having to pay the full public costs for their projects. During the boom years, commissioners waived development fees for rural areas such as Gibsonton to spur growth. County standards on some roads were lowered, so until 2004 developers were excused from paying to widen them. Commissioners also kept impact fees so low that consultants concluded they didn't come close to covering the costs that development imposed on roads, the environment and schools.

Any overhaul of that system was bound to stoke some interest among developers — and it did.

Many were chagrined to learn from Planning and Growth Director Peter Aluotto that the new fees wouldn't necessarily replace impact fees.

Mike Peterson, an Apollo Beach land use attorney, said he didn't want his clients to pay both.

"I'm stunned to hear we would pay impact fees along with mobility fees," Peterson said.

The new fees would replace what the state has required developers to pay since 1985, which is for the amount of traffic their projects produce.

That was upended earlier this year when state lawmakers passed Senate Bill 360, which is meant to help the development industry by making it easier to build. It extends the life of building permits by two years and steers development to broadly defined areas that in many cases are rural and could lead to more sprawl.

The bill didn't explain how developers would pay for future growth, but tucked in the bill is something called a "mobility fee." What these fees are the bill doesn't explain. Instead, it authorized the state to pay the Center for Urban Transportation Research at the University of South Florida to research what they could be.

The state paid CUTR $216,000 to study the fees. It produced a report this month that identified two ways to charge a mobility fee, one of which Hillsborough County planners were already considering.

One charges developers not for the amount of traffic a project creates, but for the average length of trips taken by those who would live, work or shop at new projects.

It's so early in the process of creating the new fees, however, that there are more questions than answers. State lawmakers could decide that the mobility fee will be statewide, making Hillsborough's fee moot, or they could decide there won't be any new fees.

Hillsborough planners will hold workshops with developers until June, then have commissioners consider them. It won't be until 2012 that they'd even be charged, if they are approved at all.

"Where it will end up, it's hard to tell," said Aluotto.

Paying the bill

A proposed "mobility" fee would developers pay for the length of average vehicle trips generated by new communities. That means it would be more expensive to build in rural Hillsborough County, where homeowners would have to drive greater distances to shop, work and play. Here's a sample of what builders would pay, on average, for a single-family home. These figures do not include other impact fees.

University Area: $6,853

Brandon: $13,738

New Tampa: $15,164

Lutz: $15,464

Wimauma: $39,752

Source: Hillsborough County Planning & Growth Management Department

Paying the bill

Here's a sample of what builders would pay, on average, for a single-family home. These figures do not include other impact fees.